JP2528693B2 - Polymer battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention uses lithium or a lithium alloy for a negative electrode,
The present invention relates to an all-solid-state polymer battery using a specific conductive polymer for a positive electrode.

[Conventional technology]

Conventionally, in a polymer battery using a conductive polymer as a positive electrode, anions in the electrolyte are doped in the conductive polymer,
Since charging and discharging were performed by dedoping,
A liquid electrolyte was indispensable for battery construction [eg, J. Electrochem. Soc., 128, 1651 (1981)].

Under such circumstances, attempts have been made to obtain a polymer battery of a solid electrolyte system, but in the past, what has been attempted is to use polypyrrole as a positive electrode and form a complexed product of polyethylene oxide and LiClO ₄ . Was used as the electrolyte and lithium was used as the negative electrode, but this one had a large internal resistance, and because the dopant was obtained from the electrolyte, sufficient electric capacity could not be obtained [Petr Novak JE
lectrochem.Soc., 134, No. 6, 1341 (1987)].

[Problems to be Solved by the Invention]

Since the present invention requires a liquid electrolyte in the conventional polymer battery as described above, in practical use, a strong metal outer casing is required to enclose the liquid electrolyte, and therefore, the flexibility is required. However, it lacks flexibility in shape, ease of sealing, and lightness. In addition, when attempting to use solid electrolyte polymer batteries, only batteries with large internal resistance and small electric capacity could be obtained, making them practical. It is an object of the present invention to solve the problem that was lacking and to provide an all-solid-state polymer battery having practicality.

[Means for Solving the Problems] The present invention uses a complexed product of a conductive polymer and a polymer anion for a positive electrode, thereby causing doping and dedoping of lithium ions at the positive electrode, and conductivity of anions in the electrolyte. Eliminates the need to dope or de-dope the volatile polymer,
In the electrolyte, only the function of the lithium ion supplied from the negative electrode as a conductor can be fulfilled, the solid polymer electrolyte can be used, and the all solid polymer battery can be obtained.

In the present invention, as the conductive polymer forming the complex-forming product used for the positive electrode, for example, polyaniline, polythiophene, polypyrrole, polyacetylene, etc. are used. On the other hand, examples of the polymer anion include polyvinyl sulfonic acid and the general formula (I). (In the formula, when x + y = 1.0, y is 0.1 to 1.0, X is SO ₃ H or COOH, and Rf is CF ₂ , O—CF ₂ , O — (— CF ₂ ) ₃
Or And a fluorinated polymer anion represented by the general formula (II) (In the formula, when x + y = 1.0, y is 0.1 to 1.0, and X is SO ₃ H or COOH) and the like. That is, as the complexed product of the conductive polymer used for the positive electrode and the polymer anion, for example, a conductive polymer such as polyaniline, polythiophene, polypyrrole, polyacetylene, and polyvinyl sulfonic acid,
A complexed product with a polymer anion such as the fluorinated polymer anion represented by the general formula (I) and the fluorinated polymer anion represented by the general formula (II) is used.

In the complexed product of the conductive polymer and the polymer anion as described above, the polyvinyl sulfonic acid or the fluorinated polymer anion has a sulfone group (-SO
₃ H) and a carboxyl group (-COOH), these acid moieties are doped with lithium ions (Li ⁺ ions) to neutralize the acid, resulting in the discharge reaction of the battery (this Li ⁺ ion The conductive polymer and the polymer anion dissociate from the complex by the dope), and the charging reaction of the battery occurs by the Li ⁺ ion dedoping from the acid portion (the dedoping of the Li ⁺ ion gives the conductive polymer Re-complexes with the polymer anion). Therefore, when using the complexed product of the conductive polymer and the polymer anion in the positive electrode, the anion in the liquid electrolyte does not need to be doped into the polymer of the positive electrode and dedoped, and the electrolyte dissociates from the negative electrode Li ⁺ ion It suffices that the lithium salt functions only as the conductor, and it is not necessary to dissolve the lithium salt in an amount corresponding to the active material in the liquid electrolyte. Therefore, it is not necessary to use a liquid electrolyte, and a solid electrolyte can be used.

The polymer solid electrolyte is obtained by reacting, for example, an ethylene oxide-propylene oxide copolymer with a trihydric alcohol and a bifunctional organic substance such as 2,4-tolylene diisocyanate which functions as a crosslinking agent. Complex of crosslinked polymer and lithium salt, complex of polyethylene oxide and lithium salt,
Composite of polypropylene oxide and lithium salt, composite of ethylene oxide-propylene oxide copolymer and lithium salt, polyethylene oxide or polypropylene oxide, trihydric alcohol and the above 2,4-
A complex of a crosslinked polymer obtained by reacting an organic compound having a bifunctionality such as tolylene diisocyanate with a lithium salt, or Japanese Patent Application No. Sho 62-filed by the present applicant.
-Polyether glycols such as polyethylene oxide, polypropylene oxide, ethylene oxide-propylene oxide copolymers disclosed in No. 265806 and
A complex of a crosslinked polymer and a lithium salt, which is obtained by reacting a bifunctional organic compound such as 2,4-tolylene diisodianate with a polyhydric alcohol having a valence of 4 or more, and Japanese Patent Application No. 62-265809. And a trihydric or higher polyhydric alcohol in which a part of the OH group is blocked by a reaction with polyethylene glycol monomethyl ether. A complex of a crosslinked polymer and a lithium salt obtained by the reaction, and a general formula (III) obtained by adding polyether glycol to polyglycerol disclosed in Japanese Patent Application No. 62-265810. (In the formula, R is polyethylene glycol, polypropylene glycol, or ethylene oxide-propylene oxide copolymer, and n is 2 to 50) A composite of a cross-linked polymer and a lithium salt, which is cross-linked with a cross-linking agent. , A general formula (IV) obtained by vinyl-polymerizing an allylated polyether glycol disclosed in Japanese Patent Application No. 62-265811. (In the formula, R ₁ is H or CH ₃ , l is ₃ to 360, and m is 2
A complex of a polymer obtained by cross-linking the polymer represented by the formula (4) with a cross-linking agent and a lithium salt. And, as the lithium salt used to form the composite with the conductive polymer, for example, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiBr, LiI, LiS
Examples include CN, LiBF ₄ , LiClO ₄ , and LiAsF ₆ .

In the present invention, in order to use the complex-formed product of the conductive polymer and the polymer anion as a positive electrode, the powder of the complex-formed product is usually pressure-molded into a pellet or a sheet. At that time, a binder such as polytetrafluoroethylene may be added to the complex-forming product. Further, when a solid polymer electrolyte is added to the complexed product of the above-mentioned conductive polymer and polymer anion to form a molded body, which is used for the positive electrode, the ionic conductivity inside the positive electrode is improved and the internal resistance is reduced. Therefore, it is particularly preferable.

Lithium or a lithium alloy is used for the negative electrode.
Examples of the lithium alloy include lithium-aluminum alloy, lithium-tin alloy, lithium-zinc alloy, lithium-lead alloy, lithium-bismuth alloy, lithium-
A silicon alloy, a lithium-antimony alloy, a lithium-magnesium alloy, a lithium-indium alloy, a lithium-gallium alloy, a lithium-germanium alloy, a lithium-gallium-indium alloy, or the like is used. Further, those obtained by adding another metal to these lithium alloys can also be used for the negative electrode.

〔Example〕

Example 1 Ethylene oxide - acetone crosslinked polymer obtained by reacting propylene oxide copolymer and the glycerol and 2,4-tolylene diisocyanate, a LiCF ₃ SO ₃ was dissolved at a concentration of 1mol / acetone solution Soak in
In the above-mentioned polymer, LiCF was added to 15 ethylene bonds of the ethylene oxide-propylene oxide copolymer part.
_A solid polymer electrolyte was obtained by complexing ₃ SO ₃ at a rate of one. The solid polymer electrolyte expressed as triol _{(PEO-PPO) -LiCF 3 SO} 3 polymer solid electrolyte in the following.

Next, the anion was dissolved in an aqueous solution in which polyvinyl sulfonic acid was dissolved, and (NH ₄ ) ₂ Cr ₂ O was added as an oxidant in the solution.
₇ Aqueous solution was added to polymerize aniline to obtain a complex-formed product of polyaniline and polyvinyl sulfonic acid.

After mixing at a ratio of 70:30 and complexing of the said polyaniline and polyvinyl sulfonic acid, and said triol _{(PEO-PPO) -LiCF 3 SO} 3 polymer solid electrolyte in a weight ratio of 80
It is heated to ℃ and made into a sheet with a thickness of 0.4 mm.
It was punched out into m to obtain a positive electrode. The triol _{(PEO-PPO) -LiCF 3 SO} 3 based solid polymer thickness 0.1m electrolyte in the electrolyte
A battery (model cell) shown in FIG. 1 was prepared using a sheet made into m and punched out to have a diameter of 10 mm, and using a lithium plate having a thickness of 0.1 mm and a diameter of 10 mm as a negative electrode. First
In the figure, 1 is the above positive electrode, 2 is an electrolyte, and 3 is a negative electrode. 4 and 5 are current collectors, 6 and 7 are lead wires, 8 is a polypropylene cell container, and 9 is a polypropylene sealing body.

Example 2 A crosslinked polymer obtained by reacting polyethylene oxide with 2,4-tolylene diisocyanate was treated with LiBF ₄
Was immersed in an acetone solution in which acetone was dissolved at a concentration of 1 mol / mol, and LiBF ₄ was complexed with the above polymer at a ratio of 30 ether bonds of ethylene oxide to obtain a solid polymer electrolyte. The solid polymer electrolyte expressed as PEO-LiBF ₄ polymer solid electrolyte in the following.

Next, 5% of fluorinated ion exchange resin [Nafion (trade name) manufactured by DuPont, the structural formula of this Nafion is as described below and has a sulfone group]
2 ml of aniline was added to 40 ml of the mixture of the aqueous dispersion and 2-propanol, and the potential range on the platinum plate (20 mm x 20 mm)
0.2V to + 0.9V (SCE, SCE is a standard calomel electrode), scanning speed 100mV / sec, aniline is polymerized by electrolytic polymerization method to synthesize a complex of polyaniline and fluorinated polymer anion. did. The obtained complex-formed product was thoroughly washed with water and then vacuum dried at 50 ° C.

The weight ratio of the complexed product of the polyaniline and the fluorinated polymer anion to the PEO-LiBF ₄ system solid polymer electrolyte
After mixing at a ratio of 80:20, it was heated to 80 ° C. to form a sheet having a thickness of 0.4 mm, which was punched out to a diameter of 10 mm to obtain a positive electrode. As the electrolyte, the above PEO-LiBF ₄ polymer solid electrolyte was formed into a sheet with a thickness of 0.1 mm and punched to have a diameter of 10 mm, and used as the negative electrode, and a lithium plate with a thickness of 0.1 mm and a diameter of 10 mm was used as the negative electrode. In the same manner as in Example 1, a battery (model cell) having the structure shown in FIG. 1 was produced.

The structural formula of the fluorinated ion exchange resin Nafion (trade name) used in the polymerization of aniline is as follows.

Comparative Example 1 A composite of polyethylene oxide and LiClO ₄ (hereinafter referred to as PEO-LiClO ₄ -based polymer solid electrolyte) was used as a solid electrolyte, lithium was used for the negative electrode, and HClO ₄ was used for the positive electrode at 0.2
aniline 0.1mol / dissolved in mol / dissolved aqueous solution,
A mixture of polyaniline obtained by polymerizing by electrolytic polymerization using a platinum plate as an electrode, washed with water and dried, and the PEO-LiClO ₄ -based polymer solid electrolyte in a weight ratio of 70:30 was prepared in the same manner as in Example 1 above.
A battery (model cell) having the structure shown in FIG. The battery of Comparative Example 1 was
It is a battery produced in accordance with the above-described trial of the solid electrolyte type polymer battery. However, when polypyrrole is used as the conductive polymer, a difference between the polypyrrole and the polyaniline makes a difference in battery characteristics due to a difference in other constitution unclear.
Polyaniline is used according to.

The batteries of Examples 1 and 2 and the battery of Comparative Example 1 were
FIG. 2 shows the discharge characteristics when the battery was charged at 3.9 V at 50 ° A at 50 ° C and then discharged at 10 μA.

In addition, the batteries of Examples 1 and 2 and the battery of Comparative Example 1 were tested at 80 ° C. and 50 μA at a charge end voltage of 3.9 V and a discharge end voltage of 2.
FIG. 3 shows the cycle characteristics when charging / discharging at 0V.

In FIG. 2, the vertical axis represents the voltage and the horizontal axis represents the discharge electricity amount. As shown in FIG. 2, the discharge electricity amount until the voltage decreases to 1 V is the same as in Examples 1 to 2. The battery of 1 is much larger than the battery of Comparative Example 1. Further, in FIG. 3, the vertical axis represents the amount of electricity discharged for each cycle, and the horizontal axis represents the number of cycles. However, when compared with the same number of cycles, the batteries of Examples 1 and 2 were compared with Comparative Example 1 The discharge amount of electricity is larger than that of the battery. As described above, the batteries of Examples 1 and 2 have a large amount of discharged electricity and have sufficient battery performance in practical use as compared with the battery of Comparative Example 1 corresponding to the conventionally proposed all-solid-state polymer battery. It was

As described above, according to the present invention, it is possible to have a practical battery performance that could not be achieved by the conventional technique, even though it is an all-solid-state polymer battery that does not use a liquid electrolyte. For practical use, a strong metal thing is not required for the outer package, and the outer package need only be one that can block the outside air. For example, use a resin outer package such as a polychlorotrifluoroethylene sheet. Because it can be used, it is possible to realize an all-solid-state polymer battery that has flexibility, shape flexibility, ease of sealing and lightness, and practical battery performance. Became.

〔The invention's effect〕

As described above, in the present invention, lithium ion doping in the positive electrode, by using a complex formation product of a conductive polymer and polymer anion capable of dedoping, it is possible to use a solid polymer electrolyte as an electrolyte, An all-solid-state polymer battery could be provided.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a polymer battery according to the present invention. FIG. 2 is a discharge characteristic diagram of the batteries of Examples 1 and 2 and the battery of Comparative Example 1, and FIG. 3 is the battery of Examples 1 and 2 and Comparative Example 1
3 is a cycle characteristic diagram of the battery of FIG. 1 ... Positive electrode, 2 ... Electrolyte, 3 ... Negative electrode

Continuation of front page (72) Inventor Hiroshi Hattori 1-188, Tora, Ibaraki-shi, Osaka Inside Hitachi Maxell Co., Ltd. (56) Reference JP-A-63-39916 (JP, A)

Claims (4)

(57) [Claims] 1. A polymer battery comprising lithium or a lithium alloy as a negative electrode, a complexed product of a conductive polymer and a polymer anion as a positive electrode, and a solid polymer electrolyte as an electrolyte. 2. The polymer battery according to claim 1, wherein the positive electrode is a mixture of a complexed product of a conductive polymer and a polymer anion and a solid polymer electrolyte. 3. The polymer battery according to claim 1, wherein the conductive polymer is polyaniline and the polymer anion is polyvinyl sulfonic acid. 4. The conductive polymer is polyaniline and the polymer anion is a fluorinated polymer anion.
Alternatively, the polymer battery according to claim 2.